Yieldable gear arrangement for an interval timer



March 1961 w. 1P. GALLAGHER ETAL 2,973,659

YIELDABLE GEAR ARRANGEMENT FOR AN INTERVAL TIMER 2 Sheets-Sheet 1 Original Filed June 1, 1954 Iw -A'JMC .oli\\ N V/l m, M w Hwy/ a w 4\ .w m w 04 w 3 Q b w M a x I x r F j wm 7 INVENTORS. W PGCZ% 5 lfi'cfzroeder' March 7, 1961 W. P. GALLAGHER ETAL YIELDABLE GEAR ARRANGEMENT FOR AN INTERVAL TIMER 2 Sheets-Sheet 2 Driginal Filed June 1, 1954 INVENTORS. WflzarrzPfiaZZa 27am fi lle, 7:

2,973,659 Patented Mar. 7, 1961 YIELDABLE GEAR ARRANGEMENT FOR AN INTERVAL TIMER William P. Gallagher, Anthony Dan Stolle, and Donald E. Schroeder, Chicago, Ill., assignors to International Register Company, Chicago, Ill., a corporation of Illinois Claims. (Cl. 74-405) The present application relates to improvements in interval timers, and is divisional of our prior parent application, Serial No. 433,426, filed June 1, 1954, which issued on May 12, 1959, as Patent No. 2,886,106.

This interval timer, in the preferred embodiment herein disclosed, is associated directly with an electrically driven clock, from which it derives its operating energy; and the interval timer comprises a rotating pointer which revolves concentrically of the clock dial and clock hands of this electric clock. Also, as disclosed in the above parent Patent 2,886,106, the combined construction of electric clock and interval timer concentrically arranged, may further include a range timer construction having an adjustable stop cooking dial and an adjustable cooking hours dial, etc., both mounted for rotation concentrically of the clock dial, clock hands and interval timer pointer.

Our improved interval timer may be made to cover any desired range of selectable time intervals, depending upon the intended use of the interval timer; but in the preferred embodiment herein disclosed the interval timer can be set anywhere in a span from a few minutes up to approximately 55 minutes duration or longer. The interval timer preferably gives an audible signal upon the expiration of the present time interval; although it may perform a switch controlling operation in addition to or in lieu of the audible signalling operation, if desired.

One of the advantages of having the interval timer arranged concentrically of the clock dial and clock hands of the motor driven clock basic-assembly resides in the fact that the pointer of the interval timer sweeps over an interval timer scale which is arranged concentrically of the clock dial. Also, the time driven movement of this interval timer pointer preferably has the same clockwise direction of rotation as the clock hands. This makes the operation and setting of the interval timer more readily understandable to the housewife. Moreover, the resulting structure is of more compact overall dimension than in prior constructions in which the interval timer is located eccentrically to or on one side of the clock dial. In the abovedescribed combination units wherein the motor driven clock basic-assembly has combined therewith the improved range timer mechanism in addition to the herein-described interval timer mechanism, the resulting structure has the time indicating pointer of the interval timer and also the time selecting dials of the range timer all concentric of each other and of the clock dial, which further simplifies the setting of both, and results in a more compact construction.

Another feature or object of our improved interval timer mechanism is a unique laterally defiectable mounting of the continuously rotating time driven pinion which, in the operation of the interval timer, is adapted to transmit timed rotation to a larger driven gear mounted on the interval timer shaft. This larger driven gear is of the sector or mutilated type having a toothless idling notch in its periphery in which the time driven pinion normally has idling rotation. In the setting of the interval timer, this larger driven gear is manually rotated to bring a greater or lesser portion of its toothed periphery into mesh with the continuously rotating driving pinion for time driven operation of the interval timer shaft. This manual meshing of the mutilated driven gear with the continuously rotating driving pinion may encounter difficulties because of end-to-end abutment of the teeth of one gear with the teeth of the other gear. In our improved construction, any such difiiculties in efl'ecting a manual meshing of the gears are avoided by so mounting one of the gears, preferably the driving pinion, that this gear can be deflected laterally momentarily if there is any tendency for end-to-end abutment of the teeth in the meshing operation.

Another object of the invention is to provide interval timing mechanism of the above general description which is reliable in its operation, and which is inexpensive to construct and assemble.

Other features, objects and advantages of the invention will be apparent from the following detail description of a preferred embodiment of the invention. In the accompanying drawings illustrating such embodiment:

Figure l is a front elcvational view of such interval timer embodiment wherein the interval timer is built directly into the electric clock assembly with the interval timer pointer rotating concentrically of the clock dial and clock hands.

Figure 2 is a rear elevational view of the above.

Figure 3 is a top edge view of the combination assembly, corresponding to a view looking downwardly on the plane of the line 33 of Figure 1.

Figure 4 is a detail sectional view of the interval timer mechanism on a larger scale, showing the vibratory spring arm and hammer, the control cam and the shutoff lever, as viewed reversely to the illustration of these parts in Figure 2.

Figure 5 is a detail sectional view of the motor pinion drive to the interval timer gear, and showing the idling gap in the periphery of the interval timer gear, and

Figure 6 is an axial sectional view through the motor driven pinion showing how it can be laterally deflected to accommodate meshing with the large interval timer gear.

Referring briefly to the main parts which make up the motor driven clock basic-assembly, these comprise a clock dial 21 having the twelve conventional hour numerals 22 around its periphery. Rotating within this clock dial 21 are the hour hand 24 and the minute hand 23, the hour hand being imprinted on or otherwise carried by an hour hand dial 25a. The various parts of the motor driven clock basic-assembly, including the interval timer, are mounted on a frame structure 59 comprising a main frame plate 51 disposed in an intermediate plane of the assembly, together with a rear bearing member or plate 58. These intermediate and rear plates 51 and 58 are supplemented in most instances by a front mounting plate 71 which is secured to the main frame plate 51 by three spacing posts such as 67 and 67'. The alternating current synchronous motor is mounted on the back side of the main frame plate 51. Staked to the upper and lower portions of the frame plate 51 substantially midway between its ends are rearwardly projecting spacing posts 56 which are s cured by screws 59 (Figures 2 and 3) to the rear metallic bearing plate 58.

As fully disclosed in the aforesaid parent patent, there is provided a relatively long tubular bearing bushing or sleeve which is staked substantially centrally in the main frame plate 51 and which constitutes the main bearing support for practically all of the rotating parts that are concentric of the clock dial 21. For example, the minute hand shaft or sleeve which supports and drives the minute hand 23 passes axially through the inside of this 3 main tubular mounting hub, having internal bearing support therein. Conversely, a splined arbor which mounts and drives the hour hand 24 passes axially over the outside of this stationary mounting hub, having external bearing support thereon. The minute and hour hands 23 and 24 of the clock basic-assembly are geared together in the proper ratio by a gear train comprising the gears 181, etc., as fully disclosed in the parent patent. The time controlled drive of the synchronous electric motor 35 is transmitted to the clock hands 23 and 24 through the motor pinion 175 which meshes with the largegear 168 mounted concentrically of the minute hand sleeve or arbor carrying the minute hand 23. The rotation of this large gear 168 is transmitted to the clock train gearing and to the aforesaid minute hand arbor through a suitable friction slippage clutch so as to permit manual setting of the clock hands 23 and 24 in either direction without having to drive back through any of the reduction gearing in the synchronous electric motor unit 35. The manual setting of the clock hands is adapted to be performed through a laterally disposed knob 31a connecting with a setting pinion 142a meshing with the gear 183 which drives through pinion 185 to the clock train gear 181, whereby manual rotation of said knob 31a can be made operative to set the clock hands through the train of reducing gearing which connects the minute hand with the hour hand. The clock hands are usually covered by a conventional cover glass 43. The foregoing elements and parts constitute the major portion of the motor driven clock basic-assembly.

Referring now to the parts of our improved interval timer mechanism constituting the subject matter of the present application, these include a separate interval timer pointer 41 which is mounted on an interval timer shaft 42 (Figures 4 and 5) which extends axially through the assembly of clock hands and their associated tubular driving shafts or sleeves. The front end of this interval timer shaft 42 extends out through a central aperture in the cover glass 43 which covers the time indicating hands 2324, the outer end of this interval timer shaft being provided with a setting knob 45 by which the interval timer may be set. The interval timer pointer 41 cooperates with the interval timer scale 46 of relatively large radius which surrounds the clock hands 23, 24. This interval timer scale has an Off position (designated 47), and also has a short gap 43 followed by a series of numerals and minute indicating dots ranging from zero substantially to 55 or more, the latter corresponding to the Off position 47. The progression of these time scale numerals is in a counterclockwise direction, but in the use of the interval timer the pointer 41 will be preset by rotation of the knob 45 in either direction to a particular point of the scale 46, corresponding to the length of time interval to be measured, following which the pointer 41 will thereafter rotate in a clockwise direction in returning back to its Off position. The arrangement of the interval timer shaft 42, knob 45, pointer 41 and scale 46 concentrically of the clock dial 21 and clock hands 23, 24 has the aforementioned advantages of a more simplified operation and a more compact construction.

Referring now to the more specific details of the interval timer mechanism, this is preferably of the electric magnetic buzzer type which will start to sound upon the expiration of the preselected time interval, and will continue to sound until shut off. As shown in Figures 2 and 4, it comprises a vibratory reed or spring arm 291 carrying a hammer or armature 292 at its vibrating end which is adapted to respond to the alternating current electromagnetic field generated in the stator of the synchronous motor 35. The spring arm or reed 231 is preferably constructed as an integral part of the metallic bearing plate 58, the spring arm being integrally joined at its stationary end with the bearing plate through the connecting web 293, from which it will be seen that the spring arm is punched out as an integral extension of the bearing plate 58 in the same plane therewith, and is thereafter bent to a position at right angles to the edge of this bearing plate. This integral construction also affords a lower reluctance magnetic path from the vibratory reed through the bearing plate 58, screws 59, spacing posts 56 and metallic frame plate 51 to the lower side of the housing 177 of the synchronous motor 35. The hammer or armature 292 extends through a slotted opening in the upper portion of the motor housing, and is arranged to be vibrated by alternating current electromagnetic flux emanating from the stator winding of the synchronous motor. In this regard, the internal construction of the synchronous motor may be modified to cooperate with the vibratory buzzer assembly 291, 2.92 in the manner disclosed in the copending application of William P. Gallagher and Paul G. Bielik, Serial No. 421,396, filed April 6, 1954, issued June 26, 1956, as Patent 2,752,592, for obtaining a more efficient construction.

The vibratory reed and hammer are normally held suppressed against vibration through a relatively thin deflecting reed 297 which is secured to the vibrating end of the spring arm 291 and extends outwardly therefrom beyond this end. This vibration suppressing reed may be secured to the spring arm 291 by forming the hammer or armature 292 with the narrowed shank portion 292' which is passed through aligned slots in the suppression reed and in the spring arm and is staked over on the back side of the spring arm. The suppression spring 297 is normally held deflected inwardly toward the synchronous motor to hold the hammer or armature 292 pressed inward resiliently under snfficient pressure to prevent its audible vibration. This normal, non-sounding position of the vibrator assembly is maintained by a shut-off lever 301 which is pivotally mounted on a pivot pin 302 carried by the frame plate 58. The outwardly extending arm of this lever is formed with a laterally bent lug 303 which normally bears against the back side of the suppression spring 297 for resiliently holding the latter deflected inwardly toward the motor 35. The other arm of the shut-off lever carries a pin 304 which projects inwardly or forwardly of the frame plate 58 for cooperation with a cam wheel 305 arranged to be manually rotated by the internal timer 42. This cam wheel 305 is staked to one end of a mounting hub 306, to the other end of which is staked a spur gear 307 of the sector or mutilated type having a toothless idling notch at one point in its periphery, as will be later described. The hub 306 is fixedly anchored to the rear portion of the interval timer shaft 42, the extremity of such shaft extending beyond the assembly 3053 07 for bearing mounting in an aperture in the rear frame plate 58.

Referring more particularly to the peripheral formation of the cam wheel 305, it will be seen from Figure 4 that it is formed with two closely spaced humps, 311 and 312, defining a notch 313 therebetween of substantially the same radius as the main peripheral portion of the cam wheel. The pin 304 which projects from the shut-off lever 301 normally sets in this notch 313, in which position of the pin the shut-01f lever is deflected to hold the suppression spring pressed inwardly toward the motor in the non-sounding position of the interval timer. When the pin 304 is in this notch 313, the pointer 41 stands in the vertical position pointing to the Off designation on the interval timer scale 46. Spaced in a cloc wise direction immediately beyond the notch 313 and trailing hump 312, is a relatively deep notch 314 in the cam wheel 305 which permits the tripping pin 304 to move inwardly to a smaller radius of the cam wheel than the periphery 315 and notch 313. When the pin 304 drops into the notch 314 it permits the shut-off lever 301 to retract to an inoperative position, out of engagement with the suppression reed 297. Thereuponthe buzzer vibrator begins to sound, and will continue to sound until the interval timer knob 45 is turned clockwise through the relatively short angular distance necessary to swing the pin 304 out of the deep notch 314 into the relatively shallow notch 313. When the deep notch 314 is in registration with the pin 304 the pointer 41 of the interval timer is substantially in registration with the point on the interval timer scale 46.

Referring to Figure 5, it will be seen that the gear 307 which transmits the timed drive to the interval shaft 42 is provided with an idling gap or arcuate space 321 in its periphery which is devoid of gear teeth 322. When the interval timer is set for operation, the gear teeth 322 are placed in mesh with the gear teeth 323 of a pinion 324 mounted on the drive shaft 176 which projects from the gear housing 177 of the electric motor unit 35. In the normal non-operative setting of the interval timer, the idling notch 321 is in registration with the teeth 323 of the driving pinion 324, so that no rotation is transmitted to the gear 307. As soon as the interval timer knob 45 is rotated in a clockwise direction to give a setting to the interval timer, the teeth 322 of the large gear 307 are rotated into mesh with the driving pinion teeth 323, the latter normally rotating continuously in a counterclockwise direction, as viewed from the front in Figure 4. The number of teeth 322 on the large gear which are thus manually turned into mesh with the driving pinion teeth 323 will depend upon the direction of setting rotation given the knob 45, and upon the length of time interval; i.e. if the knob 45 is rotated clockwise and if a long interval time is set, such as 50 minutes, only a few of the teeth 322 beyond the end 321 of the idling notch 321 are rotated into mesh with the driving pinion 324, whereas if a relatively short time interval is set up, such as minutes, the majority of the teeth 322 are revolved through the line of mesh with the driving pinion, so that the point of mesh in such setting is near the opposite end 321" of the idling gap 321. The angular span between the points 321' and 321" of the idling gap 321 corresponds to the angular span between the 0 point and the 01f point on the interval timer scale 46. That is to say, at the expiration of the preset time interval, when the deep notch 314 in the cam wheel comes into registration with the pin 304, the shut-oif lever 301 is permitted to swing in such direction as to remove the back pressure against the suppression spring 297 and permit the vibrator spring and hammer to start vibrating. At the same time that the deep notch 314 moves into registration with the pin 304, the leading end 321" of the idling gap 321 comes into registration with the line of mesh between the pinion 324 and gear 307. Accordingly, the interval timer gear 307 ceases rotation, and continues to remain in this position as long as the housewife permits the interval timer to sound. When the housewife wishes to turn off the sounding of the interval timer she rotates the knob 45 to turn the interval timer pointer 41 into the vertical Off position. This rotates the cam wheel 305 in a clockwise direction through just the suflicient angular distance to force the pin 304 out of the notch 314 and up over the hump 312 for dropping into the shallow Off notch 313. The resulting downward movement given to the pin 304 swings the shut-off lever 301 in a clockwise direction (Figure 4) for bringing the lug 303 to bear against the back of the suppression spring 297 and thereby silence the vibrato-r. The interval timer gear 307 was advanced correspondingly with the cam wheel 305, but, as previously described, the angular span of the idling gap 321 is such that the trailing end 321 of the gap is still in registration with the pinion 324 so that no further driving rotation is transmitted to the gear 307. When the housewife wishes to set up a desired time on the interval timer she rotates the knob 45 in a clockwise direction or in a counterclockwise direction, as desired to bring the pointer 41 .into registration with the marking of the desired time interval on the interval timer dial 46. Let us say, for example, that she desires to set the interval timer for a relatively short time interval of 5 minutes; she thereupon rotates the pointer into registration with the numeral 5, which is the position of the pointer shown in Figure 1. Such rotation of the pointer correspondingly rotates the cam wheel 305 and gear wheel 307, the positions of these two wheels shown in Figures 4 and 5 corresponding substantially to this 5 minute setting which the housewife has just given the interval timer pointer. From here on the time driven rotation of the gear wheel 307 and cam wheel 305 produce the sequence of events previously described.

Obviously, when the housewife imparts these setting adjustments to the interval timer through the knob 45, the drive pinion 324 must be capable of friction slippage or other temporary freedom of rotation relatively to the synchronous motor 35, in order to permit such setting of the large interval timer gear 307. This is preferably accomplished by the provision of a friction slippage clutch arrangement effective between the pinion 324 and the motor driven shaft 176. In our improved construction herein disclosed, we have combined with this friction slippage clutch arrangement a unique laterally deflectable mounting of the drive pinion 324 which permits this pinion to be deflected laterally in an outward direction from the gear 307; whereby, if there is any tendency for jamming between the teeth 322 on the large gear and the teeth 323 on the driving pinion because of end-to-end abutment between these teeth as the large gear is turned past the idling notch, such jamming will be avoided by the momentary lateral deflection of the pinion 324 to permit its teeth 323 to slip into the proper tooth spaces between the large gear teeth 322. As shown in Figure 6, the pinion 324 is formed with a raised hollow hub 325 which extends axially beyond the plane of the pinion teeth 323. This extended hub 325 has a large diameter cylindrical bore 326 therein which has a full size opening at its lower end (i.e. its end adjacent the pinion teeth), and which is substantially closed at its upper end by a transverse end wall 328. A central opening 329 in this end wall 328 has a relatively loose fit over the motor driven shaft 176 for the purpose of permitting cocking movement of the pinion relatively to the shaft. Extending up into the enlarged bore 326 is a conically shaped driving support 339 which rotates concurrently with the motor shaft 176. The large end of this conical member 339 has a rather close fit in the closed end of the bore 326, this large end of the cone having a flat end surface adapted to have frictional driving engagement against the inner surface of the transverse end wall 328. Fitting over the motor shaft 176 is a friction drive washer 343 which is maintained in frictional driving engagement with the outer surface of the transverse end wall 328 by a compression spring 346. The outer end of the compression spring 346 is held on the motor shaft 176 by an outer confining washer 347. It will thus be seen that the drive from the motor shaft 176 to the pinion 324 is solely through the frictional slippage surfaces or clutch construction established between the outer surface of the conical member 339 and the inner surface of the end wall 323, and also between the outer surface of the transverse end wall 328 and the inner surface of the friction washer 343, these friction slippage surfaces being maintained in spring pressed engagement at all times by the action of the compression springs 346.

Referring now to the ability of the pinion 324 to be displaced or cooked sidewise in the event of jamming between the pinion teeth 323 and the gear teeth 322, it will be seen that the reduced neck portion 351 of the conical support 339 lies at the outer end of the enlarged cylindrical bore 326. This reduced neck portion 351 permits the toothed end of the pinion hub to be cocked or tilted inwardly at an angle to the axis of the motor shaft, substantially as indicated in dotted lines in Figure 6. This enables the teeth 323 of the driving pinion 324 to be displaced away from the teeth 322 of the driven gear 307 a sufficient distance to prevent jamming as a result of end-to-end tooth contact, such lateral displacement of the pinion teeth permitting the necessary slippage between teeth to effect proper meshing. In this lateral cocking of the pinion, the flat inner surface of the trans verse end wall 328 tips up at an angle relatively to the flat end surface of the conical support 339, but immediately upon proper mesh being established between the gear teeth of the two wheels, the Pinion is restored to its normal axially aligned position by the action of the spring 346 forcing the transverse end wall 328 down into friction slippage engagement with the flat end wall of the conical support 339. This conical support 339 may be keyed or anchored to the motor shaft 176 in any desired manner and independently of any other elements on this motor shaft. However, for the purpose of reducing manufacturing and assembly costs, we preferably make this conical support 339 as an integral upward extension of the drive pinion 175 which has a keyed or drive fit on the motor shaft at 353. Thus, it will be seen that the above described construction provides the desired friction slippage clutch relation between the motor shaft 176 (or other drive shaft) and pinion 324, and also provides a resilient or yielding mounting of the pinion 324 on the motor shaft, or other drive shaft, of such nature as to permit the pinion to be deflected relatively to the motor shaft in the event of any jamming tendency between the pinion teeth and the teeth on the driven gear 322.

While we have illustrated and described what we regard to be the preferred embodiment of our invention, nevertheless it will be understood that such is merely exemplary and that numerous modifications and rearrangements may be made therein without departing from the essence of the invention.

We claim:

1. In apparatus of the class described, the combination of a driving shaft which rotates continuously at a substantially constant rate, a driving spur pinion mounted concentrically on said shaft and driven thereby, a driven shaft, a driven spur gear mounted concentrically on said driven shaft and operative to drive the latter, said driven spur gear being adapted to be driven by said driving spur pinion when in mesh therewith, said driven spur gear having a toothless idling gap in part of its periphery which normally lies in registration with said driving spur pinion so that normally there is no meshing relation between said pinion and gear and said driven shaft normally stands in an inert condition while said driving shaft rotates continu ously, a manually rotatable knob mounted on said driven shaft and operative to rotate said shaft in either direction of rotation for rotating said driven spur gear out of said normal non-meshing position so as tomanually mesh the spur teeth at either end of said idling gap in said driven gear with the spur teeth of said driving pinion, said knob being then further rotated to revolve said driven gear to an angular position corresponding to a preset desired degree of driving rotation to be transmitted from said driving spur pinion to said driven spur gear, suoh manual rotation of said driven gear causing corresponding rotation of said driving pinion after mesh is established between said driven gear and driving-pinion, a friction slippage clutch interposed between said driving spur pinion and said driving shaft to permit such rotation of said driving pinion in the manually operated presetting rotation of said driven gear, said driving spur pinion thereafter rotating said driven spur gear and said driven shaft at a substantially constant rate back to said normal nonmeshing position, following which said manually rotatable knob is adapted to be manually rotated to restore said driven spur gear to its normal non-meshing position, and spring pressed mounting means resiliently mounting said driving pinion on said driving shaft for permitting said driving pin-ion to assume an inclined position with its axis tilted at an angle to the axis on the driving shaft on which it is mounted in the event that there should be momentary end-to-end jamming abutment between the spur gear teeth on said driving pinion and the spur gear teeth on said driven gear in the aforesaid manually operated performance of rotating the toothless idling gap of the driven gear out of registration with the driving spur pinion for causing meshing relation between said driving pinion and driven gear, said spring pressed mounting means and said driving pinion cooperating to permit said driving pinion to assume such inclined position in the event of tooth jamming irrespective of the direction in which said manually rotatable knob is revolved.

2. In apparatus of the class described, the combination of a substantially constant speed continuously rotating driving shaft, a driving spur pinion driven by said shaft, a driven shaft, a driven spur gear operative to transmit rotation to said driven shaft and adapted to be driven by said driving spur pinion when in mesh therewith, said driven spur gear having a toothless idling gap in its periphery which normally lies in registration with said driving spur pinion so as to normally prevent driving relation from said driving pinion to said driven gear, a manually rotatable knob mounted on said interval timer shaft and operative to rotate said latter shaft in either direction of rotation for revolving said driven spur gear out of said normal non-meshing position for effecting manual meshing of the spur teeth of said driven gear at either end of said idling gap with the spur teeth of said driving pinion, whereupon said knob is then further rotated to revolve said driven gear to an angular position corresponding to a preset degree of driving rotation which it is desired to have said driving spur pinion transmit to said driven spur gear, following which manual preselecting operation said driving spur pinion automatically starts rotating said driven spur gear and said driven shaft at a substantially constant rate back to said non-meshing position, and combined spring pressed mounting means and slippage clutch means, said spring pressed mounting means resiliently mounting said driving spur pinion concentrically on said driving shaft with the axis of said driving pinion coincident with the axis of said driving shaft, said spring pressed mounting means functioning in the event of endto-end tooth abutment between said pinion and gear in the manual rotation of said toothless idling gap out of registration with said driving pinion to permit the axis of said driving pinion to move into an angular position inclined relatively to but intersecting the axis of said time driven shaft, whereby momentary slippage can occur between the abutting gear teeth, said spring pressed mounting means permitting the axis of said driving pinion to move into such angular position irrespective of the direction of rotation of said manually rotatable knob, said spring pressed slippage clutch means permitting slippage rotation of said driving pinion relatively to said time driven shaft.

3. In apparatus of the class described, the combination of a driving shaft which rotates continuously at a substantially constant rate, a driving gear driven thereby, a driven shaft, a driven gear for rotating said driven shaft, said driving gear being adapted to drive said driven gear when meshing relation is established therebetween, said drivengear having a toothless idling gap therein which normally lies in registration with said driving gear so as to normally prevent meshing relation between said gears, manually operated means rotatable in either direction of rotation for manually rotating said driven gears so as to cause meshing of the teeth of said driven gear at either end of said toothless idling gap with the teeth of said driving gear, following which the manually operated means is then further rotated to revolve said driven gear to an angular position corresponding to a preset degree of reverse driving rotation which it is desired to have said driving gear transmit to said driven gear, and spring pressed mounting means for said driving gear permitting said driving gear to assume a tilted position in the event of tooth jamming during the operation of effecting manual meshing between said gears, said spring pressed mounting means permitting such tilting of said driving gear in the event of the aforesaid tooth jamming between the gears irrespective of the direction of rotation of said manually operated means during the operation of eifecting manual meshing between said gears, said driving gear driving said driven gear back to an operative position after the driven gear has been manually set up into a position corresponding to the preset degree of reverse rotation which it is desired to have said driving gear transmit to said driven gear.

4. In apparatus of the class described, the combination of a driving shaft which rotates continuously at a substantially constant rate, a driving gear driven thereby, a driven shaft, a driven gear operative to impart rotation to said driven shaft, said driving and driven gears being operative to transmit rotation therebetween When in meshing relationship, said driven gear having a toothless idling gap therein which normally lies in registration with said driving gear so as to normally prevent meshing relationship between said gears, a manually rotatable knob operatively connected for rotating said driven shaft and driven gear for manually meshing the teeth of said driven gear at one end of the toothless idling gap with the teeth of said driving gear, said knob being thereafter further rotated to revolve said driven gear to an angular position corresponding to a preset degree of reverse driving rotation which it is desired to have said driving gear transmit to said driven gear, following which said driving gear automatically rotates said driven gear and driven shaft back towards their normal positions, said driving gear having a tiltable mounting on said driving shaft, and spring pressed mounting means resiliently holding said driving gear concentric with respect to said driving shaft with the axis of said driving gear coincident with the axis of said driving shaft, but in the event of end-to-end tooth abutment between said gears during the manually performed operation of rotating said toothless idling gap out of registration with said driving gear, permitting the axis of said driving gear to move into an angular position inclined relatively to but intersecting the axis of said driving shaft whereby to permit momentary slippage between the teeth of the driven and driving gears, said driving gear being operative to drive said driven gear back to an operative position upon the termination of the preset degree of reverse rotation.

5. In apparatus of the class described, the combination of a driving shaft and a driving gear driven thereby, a driven shaft and a driven gear operative to rotate said driven shaft, said driving and driven gears being operative to transmit rotation therebetween when their gear teeth are in meshing relation, said driven gear having a toothless idling gap therein which normally lies in registration with said driving gear whereby no rotation is normally transmitted from said driving gear to said driven gear, manually operated means for rotating said driven gear to nullify said toothless idling gap and to bring the gear teeth of said driven gear into meshing relation with the gear teeth of said driving gear, said driving gear thereupon being operative to drive said driven gear back substantially to its normal position with the toothless idiin g gap in registration with the driving gear, a conically shaped driving support on said driving shaft having a substantially fiat frictional driving surface at its larger end, a tubular hub on said driving gear having a cylindrical bore fitting over said conical mounting member and having an end wall provided with a substantially fiat internal frictional driving surface adapted to engage with the frictional driving surface of said conical driving support, and spring means on said time driven shaft for holding said two frictional surfaces pressed together in frictional slippage clutch relationship, said spring means permitting lateral cocking movement of said driving gear and its tubular hub relatively to said conical driving support in the event of jamming of the gear teeth in the performance of the manual meshing operation to bring the toothless idling gap out of registration with said driving gear.

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